Packet sending method and apparatus based on multi-link aggregation

ABSTRACT

Embodiments of the present invention provide a packet sending method, including: receiving a packet, where the packet carries priority information indicating a priority of the packet; selecting, according to a correspondence between packet priorities and component links in a link aggregation group, a component link corresponding to the priority of the packet, where the link aggregation group includes at least a first component link and a second component link, availability of the first component link is higher than availability of the second component link, and in the correspondence between packet priorities and component links, a first priority corresponds to the first component link, a second priority corresponds to at least one of the second component link and the first component link, and the first priority is higher than the second priority; and sending the packet on the selected component link.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2015/075337, filed on Mar. 28, 2015. The disclosure of theaforementioned application is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofcommunications technologies, and in particular, to a packet sendingmethod and apparatus based on multi-link aggregation.

BACKGROUND

As network bandwidth demands grow rapidly, when a single-link bandwidthcannot meet a demand, generally, multiple physical links between twodevices are bundled as a logical link, to from a Link Aggregation Group(LAG). Service traffic is jointly borne by multiple component links inthe link aggregation group. In the prior art, service packets aresequentially scheduled, by using a Round Robin (RR) algorithm, to eachcomponent link for sending. However, when performance of a componentlink of the link aggregation group is relatively poor, efficiency andreliability of packet transmission are reduced.

SUMMARY

Embodiments of the present invention provide a packet sending method andapparatus based on multi-link aggregation, so as to overcome a problemin the prior art that efficiency and reliability of packet transmissionare reduced when performance of a component link of a link aggregationgroup is relatively poor.

According to a first aspect, an embodiment of the present inventionprovides a packet sending method. The method includes receiving apacket, where the packet carries priority information indicating apriority of the packet. The method also includes selecting, according toa correspondence between packet priorities and component links in a linkaggregation group, a component link corresponding to the priority of thepacket, where the link aggregation group includes at least a firstcomponent link and a second component link; availability of the firstcomponent link is higher than availability of the second component link;and in the correspondence between packet priorities and component links,a first priority corresponds to the first component link, a secondpriority corresponds to at least one of the second component link andthe first component link, and the first priority is higher than thesecond priority. The method also includes sending the packet on theselected component link.

In a first possible implementation manner, before the selecting,according to a correspondence between packet priorities and componentlinks in a link aggregation group, a component link corresponding to thepriority of the packet, the method further includes: sending, accordingto a correspondence between packet priorities and component fragmentunits in a fragment unit group, the packet to a component fragment unitcorresponding to the priority of the packet; and fragmenting the packetin the component fragment unit to obtain multiple fragments; where theselecting, according to a correspondence between packet priorities andcomponent links in a link aggregation group, a component linkcorresponding to the priority of the packet includes: selecting,according to a correspondence between component fragment units andcomponent links, a component link corresponding to the componentfragment unit; and the sending the packet on the selected component linkincludes: sending the multiple fragments of the packet on the selectedcomponent link.

In a second possible implementation manner of the first aspect, beforethe selecting, according to a correspondence between packet prioritiesand component links in a link aggregation group, a component linkcorresponding to the priority of the packet, the method furtherincludes: fragmenting the packet to obtain multiple fragments, where themultiple fragments carry the priority information; where the selecting,according to a correspondence between packet priorities and componentlinks in a link aggregation group, a component link corresponding to thepriority of the packet includes: selecting, according to thecorrespondence between packet priorities and component links, acomponent link corresponding to the multiple fragments; and the sendingthe packet on the selected component link includes: sending the multiplefragments of the packet on the selected component link.

With reference to the first possible implementation manner of the firstaspect, in a third possible implementation manner of the first aspect,before the selecting, according to a correspondence between packetpriorities and component links in a link aggregation group, a componentlink corresponding to the priority of the packet, the method furtherincludes: configuring the correspondence between component fragmentunits and component links according to availability of a component linkin the link aggregation group and the priority of the packet thatcorresponds to the component fragment unit.

With reference to the first possible implementation manner of the firstaspect, in a fourth possible implementation manner of the first aspect,before the selecting, according to a correspondence between packetpriorities and component links in a link aggregation group, a componentlink corresponding to the priority of the packet, the method furtherincludes: determining a priority of the component fragment unitaccording to the priority of the packet that corresponds to thecomponent fragment unit; and configuring the correspondence betweencomponent fragment units and component links according to availabilityof a component link in the link aggregation group and the priority ofthe component fragment unit.

With reference to the first possible implementation manner in the firstaspect, in a fifth possible implementation manner of the first aspect,the fragment unit group includes at least a first component fragmentunit and a second component fragment unit; and in the correspondencebetween packet priorities and component fragment units, the firstpriority corresponds to the first component fragment unit, and thesecond priority corresponds to the second component fragment unit; andin the correspondence between component fragment units and componentlinks, the first component fragment unit corresponds to the firstcomponent link, and the second component fragment unit corresponds to atleast one of the second component link and the first component link.

With reference to the first possible implementation manner of the firstaspect, in a sixth possible implementation manner of the first aspect,the sending the multiple fragments of the packet on the selectedcomponent link includes: detecting whether a traffic shaper of thecomponent link allows sending of the fragments; and if the trafficshaper of the component link allows sending of the fragments, sendingthe fragments on the component link; or if the traffic shaper of thecomponent link does not allow sending of the fragments, selectinganother component link corresponding to the priority to send themultiple fragments of the packet.

With reference to the first possible implementation manner of the firstaspect, in a seventh possible implementation manner of the first aspect,whether the packet needs to be fragmented is determined. If the packetdoes not need to be fragmented, the packet is scheduled to the selectedcomponent link.

With reference to the seventh possible implementation manner of thefirst aspect, before the determining whether the packet needs to befragmented, the method further includes: reserving a bandwidth for eachcomponent link, where the reserved bandwidth is used to send anon-fragmented packet.

With reference to the first possible implementation manner of the firstaspect, in a ninth possible implementation manner of the first aspect,the fragments carry fragment identifiers, so that a receive endreassembles the fragments according to the fragment identifiers.

According to a second aspect, an embodiment of the present inventionprovides a packet sending apparatus based on multi-link aggregation. Theapparatus includes a receiving unit, configured to receive a packet,where the packet carries priority information indicating a priority ofthe packet. The apparatus also includes a selection unit, configured toselect, according to a correspondence between packet priorities andcomponent links in a link aggregation group, a component linkcorresponding to the priority of the packet, where the link aggregationgroup includes at least a first component link and a second componentlink; availability of the first component link is higher thanavailability of the second component link; and in the correspondencebetween packet priorities and component links, a first prioritycorresponds to the first component link, a second priority correspondsto at least one of the second component link and the first componentlink, and the first priority is higher than the second priority. Theapparatus also includes a sending unit, configured to send the packet onthe selected component link.

In a first possible implementation manner of the second aspect, theapparatus further includes: a distributing unit, configured to send,according to a correspondence between packet priorities and componentfragment units in a fragment unit group, the packet to a componentfragment unit corresponding to the priority of the packet; and thecomponent fragment unit, configured to separately fragment the packet toobtain multiple fragments; where the selection unit is specificallyconfigured to select, according to a correspondence between componentfragment units and component links, a component link corresponding tothe component fragment unit; and the sending unit is specificallyconfigured to send the multiple fragments of the packet on the selectedcomponent link.

In a second possible implementation manner of the second aspect, theapparatus further includes: a fragmenting unit, configured to fragmentthe packet according to the priority of the packet to obtain fragments,where the fragments carry the priority information, where the selectionunit is specifically configured to select, according to thecorrespondence between packet priorities and component links, acomponent link corresponding to the multiple fragments; and the sendingunit is specifically configured to send the multiple fragments of thepacket on the selected component link.

With reference to the first possible implementation manner of the secondaspect, in a third possible implementation manner of the second aspect,the apparatus further includes: a configuration module, configured toconfigure the correspondence between component fragment units andcomponent links according to availability of a component link in thelink aggregation group and the priority of the packet that correspondsto the component fragment unit.

With reference to the first possible implementation manner of the secondaspect, in a fourth possible implementation manner of the second aspect,the fragment unit group includes at least a first component fragmentunit and a second component fragment unit; and in the correspondencebetween packet priorities and component fragment units, the firstpriority corresponds to the first component fragment unit, and thesecond priority corresponds to the second component fragment unit; andin the correspondence between component fragment units and componentlinks, the first component fragment unit corresponds to the firstcomponent link, and the second component fragment unit corresponds to atleast one of the second component link and the first component link.

With reference to the first possible implementation manner of the secondaspect, in a fifth possible implementation manner of the second aspect,the sending unit is further configured to: detect whether a trafficshaper of the component link allows sending of the fragments; and if thetraffic shaper of the component link allows sending of the fragments,send the fragments on the component link; or if the traffic shaper ofthe component link does not allow sending of the fragments, selectanother component link corresponding to the priority to send themultiple fragments of the packet.

With reference to the first possible implementation manner of the secondaspect, in a sixth possible implementation manner of the second aspect,the fragments carry fragment identifiers, so that a receiving endreassembles the fragments according to the fragment identifiers.

According to a third aspect, an embodiment of the present inventionprovides a packet sending device based on multi-link aggregation. Thedevice includes a communications interface, a processor, and a memory,where the communications interface, the processor, and the memorycommunicate with each other by using a bus, the memory stores anexecutable instruction, and the processor invokes the executableinstruction in the memory, to perform the following operations:receiving a packet, where the packet carries priority informationindicating a priority of the packet; selecting, according to acorrespondence between packet priorities and component links in a linkaggregation group, a component link corresponding to the priority of thepacket, where the link aggregation group includes at least a firstcomponent link and a second component link; availability of the firstcomponent link is higher than availability of the second component link;and in the correspondence between packet priorities and component links,a first priority corresponds to the first component link, a secondpriority corresponds to at least one of the second component link andthe first component link, and the first priority is higher than thesecond priority; and sending the packet on the selected component link.

In the embodiments of the present invention, a packet is received, wherethe packet carries priority information indicating a priority of thepacket; a component link corresponding to the priority of the packet isselected according to a correspondence between packet priorities andcomponent links in a link aggregation group, where the link aggregationgroup includes at least a first component link and a second componentlink, availability of the first component link is higher thanavailability of the second component link, and in the correspondencebetween packet priorities and component links, a first prioritycorresponds to the first component link, a second priority correspondsto at least one of the second component link and the first componentlink, and the first priority is higher than the second priority; and thepacket is sent on the selected component link. The embodiments candistinguish between packet priorities to select a component link usedfor sending. Therefore, a high-priority service flow can be sent on ahigh-availability link, and transmission reliability of a high-prioritypacket can be effectively ensured, thereby improving efficiency andreliability of packet transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly describes the accompanyingdrawings required for describing the embodiments of the presentinvention. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present invention, and aperson of ordinary skill in the art may still derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a scenario diagram of a microwave link according to anembodiment of the present invention;

FIG. 2 is a scenario diagram of another microwave link according to anembodiment of the present invention;

FIG. 3 is a flowchart of a packet sending method based on multi-linkaggregation according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a fragment according to anembodiment of the present invention;

FIG. 5 is a flowchart of a packet receiving method based on multi-linkaggregation according to an embodiment of the present invention;

FIG. 6 is a structural diagram of a packet sending apparatus based onmulti-link aggregation according to an embodiment of the presentinvention;

FIG. 7 is a structural diagram of another packet sending apparatus basedon multi-link aggregation according to an embodiment of the presentinvention;

FIG. 8 is a structural diagram of a packet receiving apparatus based onmulti-link aggregation according to an embodiment of the presentinvention; and

FIG. 9 is a structural diagram of another packet sending device based onmulti-link aggregation according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present invention with reference to the accompanyingdrawings in the embodiments of the present invention. Apparently, thedescribed embodiments are a part rather than all of the embodiments ofthe present invention. All other embodiments obtained by a person ofordinary skill in the art based on the embodiments of the presentinvention without creative efforts shall fall within the protectionscope of the present invention.

Fiber transmission is quite mature both in technology and in networkapplication. However, due to geographic and geomorphic limitations,transmission needs to be performed in wireless manners in many places.If a bandwidth requirement is relatively high, generally, a microwavetransmission manner is used. Currently, in applications of markets suchas base station backhaul transmission of a mobile cellular system,networking of a transmission network and a metropolitan area network, adigital relay transmission network of broadcast and television, adedicated network, and large enterprise access, microwave transmissionis relatively widely applied.

Frequency bands used by common-band microwave devices are 1.4 GHz to 2.7GHz, 3 GHz to 11 GHz, 23 GHz to 55 GHz, and the like. Currently,microwave devices using frequency bands such as E-Band and V-Band alsoemerge. Different microwave devices may use different frequency bands,and may have different structures. For example, microwave devices may bea full outdoor-type microwave device, a split-type microwave device, anda full indoor-type microwave device. For a split-type microwave device,intermediate frequency processing is performed indoors. For a fulloutdoor-type microwave device, in addition to radio frequencyprocessing, intermediate frequency processing is also performedoutdoors.

A microwave link may be formed between two microwave devices. As shownin FIG. 1, two split-type microwave devices are included. A firstmicrowave device includes an Indoor Unit(IDU) 101 a, an OutdoorUnit(ODU) 102 a, and an antenna 103 a. A second microwave deviceincludes an IDU 101 b, an ODU 102 b, and an antenna 103 b. Intermediatefrequency processing is performed on a baseband signal by an IDU, andradio frequency processing is performed on the baseband signal by anODU. After such processing, the baseband signal is sent to a peer deviceby using an antenna.

A link aggregation group may be formed by two microwave links. As shownin FIG. 2, two split-type microwave devices are included. A firstsplit-type microwave device includes an IDU 101 a, an ODU 102 a 1, anantenna 103 a 1, an antenna 103 b 1, an ODU 102 b 1, and an IDU 101 b,which form a first component link. A second split-type microwave deviceincludes an IDU 101 a, an ODU 102 a 2, an antenna 103 a 2, an antenna103 b 2, an ODU 102 b 2, and an IDU 101 b, which form a second componentlink. The two microwave devices use a same IDU 101 a. In the IDU 101 a,service traffic is allocated to a component link for transmission. Thetwo microwave devices form two component links, and the two componentlinks may form a link aggregation group. In some embodiments, a linkaggregation group may be formed by three or more component links. Thecomponent link may be a microwave link, or may be a fiber link, a copperlink, or another link. A link aggregation group is a high-bandwidthlogical link, and transmits traffic on component links according to userconfigurations.

Devices that form a component link are different, and may be fulloutdoor-type microwave devices, split-type microwave devices, or fullindoor-type microwave devices, and may use different frequencies, whichmay be a common band, E-Band, V-Band, and the like. Therefore,availability of component links may differ a lot. Availability may beindicated by using degrees of availability. A degree of availability isa probability value of normally running of a microwave link within atime period or an expectation value of the probability value. As shownin Table 1, Table 1 is an example of degrees of availability.

TABLE 1 Degrees of System Type Availability Availability Unavailability(System (Availability) (Degrees of Type Unavailability) (Unit:Availability) (Unit: minute/year) percentage) Unmanaged 50,000 90(Unmanaged) Managed (Managed) 5,000 99 Well-managed 500 99.9(Well-managed) Fault-tolerant 50 99.99 (Fault-tolerant)High-availability 5 99.999 (High-availability) Very-high-availability0.5 99.9999 (Very-high-availability) Ultra-availability 0.05 99.99999(Ultra-availability)

FIG. 3 is a flowchart of an embodiment of a packet sending method basedon multi-link aggregation according to the present invention. As shownin FIG. 3, the method includes the following steps.

Step 301: Receive a packet, where the packet carries priorityinformation indicating a priority of the packet.

The received packet may be an Ethernet packet. This is not limited inthe present invention. For example, the received packet may be a packetin another encapsulation form. For example, the received packet may bean 802.3 packet, a High-Level Data Link Control (HDLC) packet, or aPoint-to-Point Protocol (PPP) packet.

Step 302: Select, according to a correspondence between packetpriorities and component links in a link aggregation group, a componentlink corresponding to the priority of the packet. The link aggregationgroup includes at least a first component link and a second componentlink. Availability of the first component link is higher thanavailability of the second component link. In the correspondence betweenpacket priorities and component links, a first priority corresponds tothe first component link, a second priority corresponds to at least oneof the second component link and the first component link, and the firstpriority is higher than the second priority.

Using FIG. 2 as an example, generally, receiving a packet and selectinga component link corresponding to a priority of the packet to send thepacket are performed in a baseband unit part of an IDU 101 a. Forexample, the first component link is selected, intermediate radiofrequency processing is performed on the packet by a transmit end on thefirst component link, and then the packet is sent to a receive antennaof a receiving end by using a transmit antenna. Then the packet is sentto a baseband unit of an IDU 101 b after intermediate radio frequencyprocessing by the receiving end, and then the packet is obtained throughrecovery.

For the packet, there may be at least two priorities, used to indicate apriority degree of the packet. For example, the priority of the packetmay be a first priority, or may be a second priority. After the packetis received, priority information of the packet may be obtained byparsing a packet header.

A high-priority packet is transmitted on a high-availability componentlink. A low-priority packet may be transmitted on a low-availabilitycomponent link. In a case in which a bandwidth of a high-availabilitycomponent link is sufficient, a low-priority packet may be transmittedon the high-availability component link. Specifically, component linksused for transmission may be determined according to a correspondencebetween packet priorities and component links. It is assumed that apossible priority of a packet is a first priority or a second priority,and the first priority is higher than the second priority. Afirst-priority packet is a packet having a requirement on availabilityof a component link, and a second-priority packet is a packet having norequirement on availability of a component link. The correspondencebetween packet priorities and component links needs to be preconfigured.For example, a link aggregation group includes a first component linkand a second component link. Availability of the first component link ishigher than availability of the second component link. The availabilityof the first component link can meet a requirement of the first-prioritypacket, and the availability of the second component link cannot meetthe requirement of the first-priority packet. The correspondence betweenpacket priorities and component links may be configured in such a mannerthat the first priority corresponds to the first component link, and thesecond priority corresponds to at least one of the second component linkand the first component link.

The priority of the packet may further include another priority. Forexample, the priority of the packet further includes a third priority.The third priority is higher than the second priority. A third-prioritypacket is a packet having a requirement on availability of a componentlink. The availability of the first component link can meet therequirement of the third-priority packet. The availability of the secondcomponent link cannot meet the requirement of the third-priority packet.The correspondence between packet priorities and component links may beconfigured in such a manner that the first priority and the thirdpriority correspond to the first component link, and the second prioritycorresponds to at least one of the second component link and the firstcomponent link.

The link aggregation group may further include another component link.For example, the link aggregation group further includes a thirdcomponent link. Availability of the third component link is higher thanthe availability of the second component link, and the availability ofthe third component link can meet the requirement of the first-prioritypacket. The correspondence between packet priorities and component linksmay be configured in such a manner that the first priority correspondsto the first component link and the third component link, and the secondpriority corresponds to at least one of the first component link, thesecond component link, or the third component link.

Step 303: Send the packet on the selected component link.

The component link corresponding to the priority of the packet isselected according to the correspondence between packet priorities andcomponent links, to send the packet. The packet may be directly sent onthe selected component link. Preferably, the packet may be fragmentedaccording to the priority to obtain fragments, and then component linksare selected to send the fragments of the packet. If the priority of thepacket corresponds to multiple component links, balanced loading of thecomponent links may be implemented. That is, loads of the componentlinks are generally the same, and the component links are fullyutilized. For example, the first priority corresponds to the firstcomponent link and the third component link. A packet has a firstpriority, and after fragmenting, some fragments of the packet aretransmitted on the first component link, and some fragments aretransmitted on the second component link, so that balanced loading canbe implemented.

Before the component link is selected, the method may specificallyinclude the following steps.

Step A: Send, according to a correspondence between packet prioritiesand component fragment units in a fragment unit group, the packet to acomponent fragment unit corresponding to the priority of the packet.

For the packet, there may be at least two priorities, used to indicate apriority degree of the packet. For example, the priority of the packetmay be a first priority, or may be a second priority. After the packetis received, priority information of the packet may be obtained byparsing a packet header.

The fragment unit group includes at least two component fragment units.A component fragment unit is configured to fragment the packet to obtainfragments. Fragment identifiers of fragments obtained by differentcomponent fragment units are different. Multiple component fragmentunits form one fragment unit group. After the priority information ofthe packet is obtained, a component fragment unit that corresponds tothe packet or component fragment units that correspond to the packet maybe determined according to the correspondence between packet prioritiesand component fragment units.

A quantity of packet priorities and a quantity of component fragmentunits may be the same, or may be different. One packet priority maycorrespond to one component fragment unit, or may correspond to multiplecomponent fragment units. Generally, one packet priority only needs tocorrespond to one component fragment unit. One component fragment unitmay correspond to one packet priority, or may correspond to multiplepacket priorities.

The correspondence between packet priorities and component fragmentunits may be preconfigured. For example, the fragment unit groupincludes a first component fragment unit and a second component fragmentunit. The correspondence between packet priorities and componentfragment units is as follows: A first priority corresponds to the firstcomponent fragment unit, a second priority corresponds to the secondcomponent fragment unit, the first priority is higher than the secondpriority, a first-priority packet is a packet having a requirement onavailability of a component link, and a second-priority packet is apacket having no requirement on availability of a component link.Certainly, the priorities may also include a third priority. Athird-priority packet is a packet having a requirement on availabilityof a component link. The third priority may correspond to the firstcomponent fragment unit. That is, the first component fragment unitcorresponds to both the first priority and the third priority.

Certainly, the fragment unit group may further include another componentfragment unit. For example, the fragment unit group includes a thirdcomponent fragment unit. The first priority may further correspond tothe third component fragment unit. That is, the first prioritycorresponds to both the first component fragment unit and the thirdcomponent fragment unit.

After a packet is received, a priority of the packet is obtained. Then acomponent fragment unit corresponding to the priority of the packet isdetermined according to the correspondence between packet priorities andcomponent fragment units. If one component fragment unit corresponds tothe priority of the packet, the packet is sent to the correspondingcomponent fragment unit. If multiple component fragment units correspondto the priority of the packet, one component fragment unit is selectedrandomly or according to a preset rule, and the packet is sent to theselected component fragment unit. Certainly, in some scenarios, ifmultiple component fragment units correspond to the priority of thepacket, the packet may be sent to all the corresponding componentfragment units. That is, the packet is sent by using a broadcastmechanism.

Step B: Fragment the packet in the component fragment unit to obtainmultiple fragments.

The packet is fragmented to obtain fragment loads. Fragments areobtained after fragment identifiers are added. The fragment identifiersinclude information about component fragment units to which the fragmentidentifiers belong, so that a receiving end identifies, according to thefragment identifiers, the component fragment units to which thefragments belong, and reassemble the fragments. Generally, the entirepacket is fragmented.

In an embodiment, a fragment identifier may include one or more of aprotocol identifier, a flow identifier, a sequence number, a startidentifier, or an end identifier.

The protocol identifier is used to identify the fragment as a packetfragment after fragmenting.

The flow identifier is used to identify a component fragment unit towhich the fragment belongs.

The sequence number is used to identify a location of the fragment.

The start identifier and the end identifier are used to identify a startfragment and an end fragment of a packet.

Specifically, as shown in FIG. 4 and the following Table 2, a packet isfragmented to obtain fragment loads. For example, a length of a fragmentload may range from 128 bytes to 512 bytes, or may be configuredautonomously according to a requirement. Then a fragment identifier isadded, and a length of the fragment identifier is 8 bytes. The fragmentidentifier includes: a protocol identifier, used to identify thefragment as a packet fragment after fragmenting, that is, a field TagProtocol Identifier (TPID), whose default value is 0x88A8, and may beconfigured according to a user's requirement; a flow identifier, used todistinguish a component fragment unit according to the bit field, wherethe receiving end reassembles fragments according to the identifier; afragment length, used to indicate a length of a fragment, in a unit ofbyte, where the length may be configured autonomously; a sequencenumber, used to identify a location of the fragment, that is, a numberof the fragment; and a start identifier and an end identifier, used toidentify a start fragment and an end fragment of the packet, that is, aStart Of Fragment (SOF) and an End Of Fragment (EOF), where “1”indicates a start fragment or an end fragment, and “0” indicates afragment that is a non-start fragment or a non-end fragment.

TABLE 2 Domain name Descriptions TPID Default value: 0x88A8, which maybe configured autonomously SID A flow identifier, used to distinguish acomponent fragment unit according to the bit field, where the receivingend reassembles fragments according to the identifier Length Indicatinga length of a fragment, in a unit of byte, where the length may beconfigured autonomously SN A sequence number, which is 14 bits, where ifthe 14 bits are occupied, the number starts from 0, and ranges from 0 to0x3fff SOP “1” indicates a start fragment, and “0” indicates a non-startfragment EOP “1” indicates an end fragment, and “0” indicates a non-endfragment

In step S302, the selecting, according to a correspondence betweenpacket priorities and component links in a link aggregation group, acomponent link corresponding to the priority of the packet includes:selecting, according to a correspondence between component fragmentunits and component links, a component link corresponding to thecomponent fragment unit.

The link aggregation group includes at least two component links. Eachlink may be a common-band microwave link, an E-Band microwave link, or aV-Band microwave link. A quantity of component fragment units and aquantity of component links may be the same, or may be different. Onecomponent fragment unit may correspond to one component link, or maycorrespond to multiple component links. One component link maycorrespond to one component fragment unit, or may correspond to multiplecomponent fragment units.

The correspondence between component fragment units and component linksmay be preconfigured. The correspondence between component fragmentunits and component links may be preconfigured according to packetpriorities that correspond to the component fragment units andavailability of the component links in the link aggregation group. Forexample, the link aggregation group includes a first component link anda second component link. Availability of the first component link ishigher than availability of the second component link. The availabilityof the first component link can meet a requirement of a first-prioritypacket, and the availability of the second component link cannot meetthe requirement of the first-priority packet. A first component fragmentunit corresponds to the first priority, and a second component fragmentunit corresponds to the second priority. The first priority is higherthan the second priority. The first-priority packet is a packet having arequirement on availability of a component link, and the second-prioritypacket is a packet having no requirement on availability of a componentlink. The correspondence between component fragment units and componentlinks may be preconfigured in such a manner that the first componentfragment unit corresponds to the first component link, and the secondcomponent fragment unit corresponds to at least one of the secondcomponent link and the first component link. In this way, it can beensured that a high-priority packet is sent on a high-availabilitycomponent link.

If the fragment unit group includes a third component fragment unit, thethird component fragment unit corresponds to the third priority, thethird priority is higher than the second priority, a third-prioritypacket is a packet having a requirement on availability of a componentlink, the availability of the first component link can meet therequirement of the third-priority packet, and the availability of thesecond component link cannot meet the requirement of the packet of thethird priority, a correspondence between component fragment units andcomponent links may be preconfigured in such a manner that the firstcomponent fragment unit and the third component fragment unit correspondto the first component link, and the second component fragment unitcorresponds to at least one of the second component link and the firstcomponent link.

Certainly, the link aggregation group may further include anothercomponent link. For example, the link aggregation group includes a thirdcomponent link. Availability of the third component link is higher thanthe availability of the second component link, and the availability ofthe third component link can meet the requirement of the first-prioritypacket. The correspondence between component fragment units andcomponent links may be preconfigured in such a manner that the firstcomponent fragment unit corresponds to the first component link and thethird component link, and the second component fragment unit correspondsto at least one of the first component link, the second component link,or the third component link.

A component fragment unit has a to-be-sent fragment. According to thecorrespondence between component fragment units and component links, ifthe component fragment unit corresponds to one component link, thecorresponding component link is used to send the fragment; or if thecomponent fragment unit corresponds to multiple component links, onecomponent link is selected to send the fragment. Certainly, the fragmentmay be simultaneously sent on the multiple component links.

A component fragment unit corresponds to a high-priority packet, and thecomponent fragment unit corresponds to a high-availability componentlink. That is, transmission of the high-priority packet is ensured.Certainly, if the component fragment unit further corresponds to alow-priority packet, component links are allocated by comprehensivelydetermining priorities corresponding to component fragment units. Abasic concept is to ensure that a high-priority packet is transmitted ona high-availability component link.

A bandwidth of a component link is limited. In this embodiment of thepresent invention, a leaky bucket algorithm may be used according to abandwidth of a component link, to perform traffic shaping on thecomponent link by using a traffic shaper, and traffic after shaping issent. The traffic shaping is intended to limit traffic flowing to thecomponent link, so that the traffic is sent to the outside at an averagespeed, so as to prevent congestion from occurring. Therefore, before acomponent link corresponding to a component fragment unit is selected tosend a fragment of the component fragment unit, whether a traffic shaperof the component link allows sending of the fragment may be detected. Ifthe traffic shaper allows sending of the fragment, the fragment is senton the component link. If the traffic shaper does not allow sending ofthe fragment, another corresponding component link may be selected tosend the fragment.

If a component fragment unit corresponds to multiple component links,one component link is selected to send a fragment. The followingprovides several component link selection methods.

a> In a Strict Priority (SP) algorithm, a link is selected according toa number of a traffic shaper. If the traffic shaper allows sending offragments, sending of the fragments continues, until a weighted value ofthe traffic shaper is used up. Actual effects are shown in the followingexample. It is assumed that a component fragment unit corresponds to twocomponent links: MAC1 and MAC2, MAC1 has a bandwidth of 100 M, and MAC2has a bandwidth of 200 M. A traffic status is as follows: If thecomponent fragment unit needs to send traffic of 100 M, MAC1 transmitsdata of 100 M, and MAC2 transmits data of 0 M. If the component fragmentunit needs to send traffic of 150 M, MAC1 transmits data of 100 M, andMAC2 transmits data of 50 M.

b> In an RR algorithm, traffic is sent by turns on each link. Actualeffects are shown in the following example. It is assumed that acomponent fragment unit corresponds to two component links: MAC1 andMAC2, MAC1 has a bandwidth of 100 M, and MAC2 has a bandwidth of 200 M.A traffic status is as follows: If the component fragment unit needs tosend traffic of 100 M, MAC1 transmits data of 50 M, and MAC2 transmitsdata of 50 M.

c> In a Weighted Round Robin (WRR) algorithm, an effect of allocatingtraffic according to a ratio of link bandwidths when there is nocongestion is achieved. Actual effects are shown in the followingexample. It is assumed that a component fragment unit corresponds to twocomponent links: MAC1 and MAC2, MAC1 has a bandwidth of 100 M, and MAC2has a bandwidth of 200 M. A traffic status is as follows: If thecomponent fragment unit needs to send traffic of 90 M, MAC1 transmitsdata of 30 M, and MAC2 transmits data of 60 M.

There is a correspondence between component fragment units and packetpriorities. Packet priorities corresponding to some component fragmentunits are high, and packet priorities corresponding to some componentfragment units are low. If multiple component fragment units need tosend fragments, differentiated scheduling may be performed. For example,fragments of high-priority packets may be preferentially scheduled, andthen fragments of low-priority packets are scheduled. For ease ofimplementation, priorities may be allocated to the component fragmentunits. If a packet priority corresponding to a component fragment unitis high, a priority of the component fragment unit is high, andfragments of the component fragment unit are preferentially scheduled.If a component fragment unit corresponds to multiple packet priorities,configuration of a priority of the component fragment unit may becomprehensively determined according to the multiple packet priorities.

In step S303, the sending the packet on the selected component link mayinclude: sending the multiple fragments of the packet on the selectedcomponent link.

Before the component link is selected, the method may furtherspecifically include the following steps.

Step A: Fragment the packet to obtain multiple fragments, where themultiple fragments carry the priority information.

In this embodiment, a packet is fragmented to obtain fragment loads, andfragments are obtained after fragment identifiers are added, where thefragment identifiers may include the priority information.

In step S302, the selecting, according to a correspondence betweenpacket priorities and component links in a link aggregation group, acomponent link corresponding to the priority of the packet includes:selecting, according to the correspondence between packet priorities andcomponent links, a component link corresponding to the multiplefragments.

For this step, refer to the foregoing embodiments.

In step S303, the sending the packet on the selected component link mayinclude: sending the multiple fragments of the packet on the selectedcomponent link.

In this embodiment, a packet is received, where the packet carriespriority information indicating a priority of the packet; a componentlink corresponding to the priority of the packet is selected accordingto a correspondence between packet priorities and component links in alink aggregation group, where the link aggregation group includes atleast a first component link and a second component link, availabilityof the first component link is higher than availability of the secondcomponent link, and in the correspondence between packet priorities andcomponent links, a first priority corresponds to the first componentlink, a second priority corresponds to at least one of the secondcomponent link and the first component link, and the first priority ishigher than the second priority; and the packet is sent on the selectedcomponent link. This embodiment can distinguish between packetpriorities to perform different fragmentation, and can select, accordingto a correspondence between component fragment units and componentlinks, a component link used for sending. Therefore, a high-priorityservice flow can be preferentially sent on a high-availability link, andwhen a bandwidth of a component link is reduced, sending of ahigh-priority service flow can be preferentially scheduled.

FIG. 5 is a flowchart of an embodiment of a packet receiving methodbased on multi-link aggregation according to the present invention. Asshown in FIG. 5, the method includes the following steps.

Step 501: Obtain packet fragments; determine, according to fragmentidentifiers of the packet fragments, a component reassembly unit towhich the packet fragments belong; and send the packet fragments to thecomponent reassembly unit, where the component reassembly unit is amember of a reassembly unit group.

Step 502: Reassemble the packet fragments in the component reassemblyunit to obtain a packet.

In this embodiment, the component reassembly unit to which the packetfragments belong is determined according to the fragment identifiers ofthe packet fragments; the packet fragments are sent to the componentreassembly unit; and the packet fragments in the component reassemblyunit are reassembled to obtain the packet, so that fragments ofdifferent fragment identifiers can be separately reassembled, and atransmit end can be effectively supported in performing differentfragmentation according to different priorities.

FIG. 6 is a schematic structural diagram of an embodiment of a packetsending apparatus based on multi-link aggregation according to thepresent invention. As shown in FIG. 6, the packet sending apparatusbased on multi-link aggregation provided in this embodiment includes: areceiving unit 601, a selection unit 602, and a sending unit 603. A linkaggregation group includes m component links 604, where m is an integergreater than 2.

The receiving unit 601 is configured to receive a packet, where thepacket carries priority information indicating a priority of the packet.

The selection unit 602 is configured to select, according to acorrespondence between packet priorities and component links in the linkaggregation group, a component link corresponding to the priority of thepacket. The link aggregation group includes at least a first componentlink and a second component link. Availability of the first componentlink is higher than availability of the second component link. In thecorrespondence between packet priorities and component links, a firstpriority corresponds to the first component link, a second prioritycorresponds to at least one of the second component link and the firstcomponent link, and the first priority is higher than the secondpriority.

The sending unit 603 is configured to send the packet on the selectedcomponent link.

If a solution of selecting a component link after a packet is fragmentedis used, as shown in FIG. 7, the apparatus may further include adistributing unit 701 and n component fragment units 702, where n is aninteger greater than 2.

The distributing unit 701 is configured to send, according to acorrespondence between packet priorities and component fragment units ina fragment unit group, the packet to a component fragment unitcorresponding to the priority of the packet.

The component fragment unit 702 is configured to fragment the packet toobtain multiple fragments.

The selection unit 602 is configured to select, according to acorrespondence between component fragment units and component links, acomponent link corresponding to the component fragment unit.

The apparatus may further include: a configuration module, configured toconfigure the correspondence between component fragment units andcomponent links according to availability of a component link in thelink aggregation group and the priority of the packet that correspondsto the component fragment unit.

The fragment unit group includes at least a first component fragmentunit and a second component fragment unit. A correspondence betweenpacket priorities and component fragment units is as follows: The firstpriority corresponds to the first component fragment unit, and thesecond priority corresponds to the second component fragment unit. Thelink aggregation group includes a first component link and a secondcomponent link, and availability of the first component link is higherthan availability of the second component link. The correspondencebetween component fragment units and component links is as follows: Thefirst component fragment unit corresponds to the first component link,and the second component fragment unit corresponds to at least one ofthe second component link and the first component link.

The sending unit 603 may further be specifically configured to: detectwhether a traffic shaper of the component link allows sending of thefragments; and if the traffic shaper of the component link allowssending of the fragments, send the fragments on the component link; orif the traffic shaper of the component link does not allow sending ofthe fragments, select another component link corresponding to thepriority to send the multiple fragments of the packet. In structure, thetraffic shaper may be a part of a first selection subunit, and eachcomponent link corresponds to a traffic shaper.

The fragments may carry fragment identifiers, so that a receiving endreassembles the fragments according to the fragment identifiers.

If a solution of selecting a component link after a packet is fragmentedis used, the apparatus may further specifically include a fragmentingunit.

The fragmenting unit is configured to fragment the packet according tothe priority of the packet to obtain fragments, where the fragmentscarry the priority information.

The selection unit 602 is configured to select, according to thecorrespondence between packet priorities and component links, acomponent link corresponding to the multiple fragments.

The sending unit 603 is configured to send the multiple fragments of thepacket on the selected component link.

The foregoing units are all logic function modules, and may beimplemented corresponding to software or hardware. Software refers tousing a micro code (micro code) of a network processor (NP), andhardware may be implemented by using an FPGA or switch chip. Forimplementation corresponding to software, the units may be invoked by aprogram or a function of the software. Corresponding to hardware, theunits may be circuit modules.

FIG. 8 is a schematic structural diagram of an embodiment of a packetreceiving apparatus based on multi-link aggregation according to thepresent invention. As shown in FIG. 8, the packet receiving apparatusbased on multi-link aggregation provided in this embodiment may be anindoor unit in this embodiment of the present invention, or an apparatusin an indoor unit, and may be configured to perform, for example, themethod shown in FIG. 3. The packet receiving apparatus includes: adistributing unit 801, and m component reassembly units 802, where m isan integer greater than 2.

The distributing unit 801 is configured to: obtain packet fragments;determine, according to fragment identifiers of the packet fragments, acomponent reassembly unit to which the packet fragments belong; and sendthe packet fragments to the component reassembly unit, where thecomponent reassembly unit is a member of a reassembly unit group.

The component reassembly units 802 are configured to reassemble thepacket fragments to obtain a packet.

The foregoing units are all logic function modules, and may beimplemented corresponding to software or hardware. Software refers tousing a micro code (micro code) of a NP, and hardware may be implementedby using an FPGA or switch chip. For implementation corresponding tosoftware, the units may be invoked by a program or a function of thesoftware. Corresponding to hardware, the units may be circuit modules.

FIG. 9 is a schematic structural diagram of an embodiment of a packetsending device based on multi-link aggregation according to the presentinvention. As shown in FIG. 9, the packet sending device based onmulti-link aggregation provided in this embodiment includes: acommunications interface 901, a processor 902, and a memory 903. Thecommunications interface 901, the processor 902, and the memory 903communicate with each other by using a bus 904. The memory 903 stores anexecutable instruction. The processor 902 invokes the executableinstruction in the memory, to perform this embodiment of the presentinvention, for example, the steps in the method shown in FIG. 3, forexample: receiving a packet, where the packet carries priorityinformation indicating a priority of the packet; selecting, according toa correspondence between packet priorities and component links in a linkaggregation group, a component link corresponding to the priority of thepacket, where the link aggregation group includes at least a firstcomponent link and a second component link; availability of the firstcomponent link is higher than availability of the second component link;and in the correspondence between packet priorities and component links,a first priority corresponds to the first component link, a secondpriority corresponds to at least one of the second component link andthe first component link, and the first priority is higher than thesecond priority; and sending the packet on the selected component link.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, reference may bemade to a corresponding process in the foregoing method embodiments, anddetails are not described herein.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely exemplary. For example, the unit division is merelylogical function division and may be other division in actualimplementation. For example, multiple units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

Persons of ordinary skill in the art may understand that all or some ofthe steps of the method embodiments may be implemented by a programinstructing relevant hardware. The program may be stored in acomputer-readable storage medium. When the program runs, the steps ofthe method embodiments are performed. The foregoing storage mediumincludes: any medium that can store program code, such as a ROM, a RAM,a magnetic disk, or an optical disc.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on multiplenetwork units. Some or all of the units may be selected according toactual needs to achieve the objectives of the solutions of theembodiments.

What is claimed is:
 1. A method, comprising: receiving, by a device, apacket carrying priority information indicating a priority of thepacket; sending, by the device, according to a correspondence betweenpacket priorities and component fragment units in a fragment unit group,the packet to a component fragment unit corresponding to the priority ofthe packet; configuring, by the device, a correspondence between thecomponent fragment units and component links in a link aggregationgroup, according to availability of a component link in the linkaggregation group and the priority of the packet that corresponds to thecomponent fragment unit; selecting, by the device, a selected componentlink corresponding to the priority of the packet, according to acorrespondence between packet priorities and the component links, andaccording to the correspondence between the component fragment units andthe component links, wherein the link aggregation group comprises afirst component link and a second component link, wherein availabilityof the first component link is higher than availability of the secondcomponent link, and in the correspondence between the packet prioritiesand the component links, a first priority corresponds to the firstcomponent link, a second priority corresponds to the second componentlink or the first component link, and the first priority is higher thanthe second priority; and sending, by the device, the packet on theselected component link.
 2. The method according to claim 1, whereinbefore selecting the selected component link corresponding to thepriority of the packet, the method further comprises: fragmenting thepacket in the component fragment unit to obtain a plurality offragments; and wherein sending the packet on the selected component linkcomprises sending the plurality of fragments of the packet on theselected component link.
 3. The method according to claim 2, whereinbefore selecting the selected component link corresponding to thepriority of the packet, the method further comprises: determining apriority of the component fragment unit according to the priority of thepacket that corresponds to the component fragment unit; and configuringthe correspondence between the component fragment units and thecomponent links according to availability of a component link in thelink aggregation group and the priority of the component fragment unit.4. The method according to claim 2, wherein the fragment unit groupcomprises a first component fragment unit and a second componentfragment unit, and in the correspondence between packet priorities andcomponent fragment units, the first priority corresponds to the firstcomponent fragment unit, and the second priority corresponds to thesecond component fragment unit; and wherein in the correspondencebetween component fragment units and component links, the firstcomponent fragment unit corresponds to the first component link, and thesecond component fragment unit corresponds to the second component linkor the first component link.
 5. The method according to claim 2, whereinsending the plurality of fragments of the packet on the selectedcomponent link comprises: detecting whether a traffic shaper of theselected component link allows sending the plurality of fragments; whenthe traffic shaper of the selected component link allows sending theplurality of fragments, sending the plurality of fragments on theselected component link; and when the traffic shaper of the selectedcomponent link does not allow sending the plurality of fragments,selecting another component link corresponding to the priority to sendthe plurality of fragments of the packet.
 6. The method according toclaim 2, further comprising: determining whether the packet is to befragmented, and when the packet is not to be fragmented, scheduling thepacket to the selected component link.
 7. The method according to claim6, wherein before determining whether the packet is to be fragmented,the method further comprises: reserving a bandwidth for each componentlink, wherein the reserved bandwidth is used to send a non-fragmentedpacket.
 8. The method according to claim 2, wherein the plurality offragments carry fragment identifiers, causing a receiving end toreassemble the plurality of fragments according to the fragmentidentifiers.
 9. The method according to claim 1, wherein beforeselecting the selected component link corresponding to the priority ofthe packet, the method further comprises: fragmenting the packet toobtain a plurality of fragments, wherein the plurality of fragmentscarry the priority information; wherein selecting the selected componentlink corresponding to the priority of the packet comprises selecting,according to the correspondence between packet priorities and componentlinks, a component link corresponding to the plurality of fragments; andwherein sending the packet on the selected component link comprisessending the plurality of fragments of the packet on the selectedcomponent link.
 10. An apparatus, comprising: a receiving unit,configured to receive a packet, wherein the packet carries priorityinformation indicating a priority of the packet; a distributing unit,configured to send, according to a correspondence between packetpriorities and component fragment units in a fragment unit group, thepacket to a component fragment unit corresponding to the priority of thepacket; a configuration module, configured to configure a correspondencebetween the component fragment units and component links in a linkaggregation group, according to availability of a component link in thelink aggregation group and the priority of the packet that correspondsto the component fragment unit; a selection unit, configured to select,a selected component link corresponding to the priority of the packet,according to a correspondence between packet priorities and thecomponent links, and according to the correspondence between thecomponent fragment units and the component links, wherein the linkaggregation group comprises a first component link and a secondcomponent link, wherein availability of the first component link ishigher than availability of the second component link, and in thecorrespondence between the packet priorities and the component links, afirst priority corresponds to the first component link, a secondpriority corresponds to the second component link or the first componentlink, and the first priority is higher than the second priority; and asending unit, configured to send the packet on the selected componentlink.
 11. The apparatus according to claim 10, wherein: the componentfragment unit, is configured to fragment the packet to obtain aplurality of fragments; the selection unit is configured to select theselected component link by selecting, according to a correspondencebetween component fragment units and component links, a component linkcorresponding to the component fragment unit; and the sending unit isconfigured to send the packet on the selected component link by sendingthe plurality of fragments of the packet on the selected component link.12. The apparatus according to claim 11, wherein the fragment unit groupcomprises a first component fragment unit and a second componentfragment unit, and in the correspondence between packet priorities andcomponent fragment units, the first priority corresponds to the firstcomponent fragment unit, and the second priority corresponds to thesecond component fragment unit; and wherein in the correspondencebetween component fragment units and component links, the firstcomponent fragment unit corresponds to the first component link, and thesecond component fragment unit corresponds to the second component linkor the first component link.
 13. The apparatus according to claim 11,wherein the sending unit is further configured to: detect whether atraffic shaper of the selected component link allows sending theplurality of fragments; when the traffic shaper of the selectedcomponent link allows sending the plurality of fragments, send theplurality of fragments on the selected component link; and when thetraffic shaper of the selected component link does not allow sending theplurality of fragments, select another component link corresponding tothe priority to send the plurality of fragments of the packet.
 14. Theapparatus according to claim 11, wherein the plurality of fragmentscarry fragment identifiers, causing a receiving end to reassemble theplurality of fragments according to the fragment identifiers.
 15. Theapparatus according to claim 10, further comprising: a fragmenting unit,configured to fragment the packet according to the priority of thepacket to obtain a plurality of fragments, wherein the plurality offragments carry the priority information; wherein the selection unit isconfigured to select, according to the correspondence between packetpriorities and component links, a component link corresponding to theplurality of fragments; and wherein the sending unit is configured tosend the plurality of fragments of the packet on the selected componentlink.
 16. A device, comprising: a communications interface; a processor;and a non-transitory computer-readable storage medium; wherein thecommunications interface, the processor, and the non-transitorycomputer-readable storage medium communicate with each other by using abus; and wherein the non-transitory computer-readable storage mediumstores an executable program to be executed by the processor, theexecutable program including instructions to: receive a packet, whereinthe packet carries priority information indicating a priority of thepacket; send, according to a correspondence between packet prioritiesand component fragment units in a fragment unit group, the packet to acomponent fragment unit corresponding to the priority of the packet;configure a correspondence between the component fragment units andcomponent links in a link aggregation group, according to availabilityof a component link in the link aggregation group and the priority ofthe packet that corresponds to the component fragment unit; select aselected component link corresponding to the priority of the packet,according to a correspondence between packet priorities and thecomponent links, and according to the correspondence between thecomponent fragment units and the component links, wherein the linkaggregation group comprises a first component link and a secondcomponent link, wherein availability of the first component link ishigher than availability of the second component link, and in thecorrespondence between the packet priorities and the component links, afirst priority corresponds to the first component link, a secondpriority corresponds to the second component link and the firstcomponent link, and the first priority is higher than the secondpriority; and send the packet on the selected component link.
 17. Thedevice according to claim 16, wherein the executable program furtherincludes instructions for: determining a priority of the componentfragment unit according to the priority of the packet that correspondsto the component fragment unit; and configuring the correspondencebetween the component fragment units and the component links accordingto availability of a component link in the link aggregation group andthe priority of the component fragment unit.
 18. The device according toclaim 16, wherein the fragment unit group comprises a first componentfragment unit and a second component fragment unit, and in thecorrespondence between packet priorities and component fragment units,the first priority corresponds to the first component fragment unit, andthe second priority corresponds to the second component fragment unit;and wherein in the correspondence between the component fragment unitsand the component links, the first component fragment unit correspondsto the first component link, and the second component fragment unitcorresponds to the second component link or the first component link.